1. Field of the Invention
The present invention is directed to a catheter having a integrated measuring probe having a measurement window disposed between a preset curvature of the catheter and the catheter tip.
2. Description of the Prior Art
A catheter having a preset or permanent bend or curvature therein is described in U.S. Pat. No. 3,674,013. This catheter also includes a fiber optics means for measuring blood oxygen in the blood vessels. The fiber optics has a light exit window disposed along a side of the catheter. The light exit window lies inside the preset bend of the catheter, i.e., between the bend and the catheter tip, so as to prevent the light exit window from coming too close to the walls of the blood vessel.
Another catheter having an integrated measuring probe for introduction into the heart is disclosed, for example, in German OS 21 42 983, corresponding to U.S. Pat. No. 3,729,008. In this catheter, the blood oxygen saturation is measured by the measuring probe using reflection oximetry, to control the pacing rate of the pacemaker to which the catheter is connected. Light from a light emitting diode is laterally directed out of the catheter through a window in the catheter wall, and the light reflected by the blood, dependent upon its oxygen saturation, is measured using a photo-transistor. This type of measuring probe can supply satisfactory measured results only if the measurement window, i.e., the active surface of the measuring probe, does not lie adjacent a wall of the heart, the heart valves, or the trabeculae. This placement restriction applies not only to probes for undertaking a blood oxygen measurement, but also to other types of measurement probes, for example impedance measurement probes. This known catheter is slightly curved following introduction into the heart, however, it is left to chance as to whether the measurement window of the measuring probe comes to lie inside or outside of the curvature.
A catheter is described in U.S. Pat. No. 4,567,901 having stimulation electrodes for the atrium and ventricle, wherein that portion of the catheter which comes to lie in the atrium has a preset curvature to facilitate positioning of the catheter.